xii. CEOPS 235 



silica being thus merely an excretion. Potash and lime are also present 

 to a less extent in cereals than in other farm crops. Owing to their 

 modest demands for potash, lime and nitrogen, cereals will grow for 

 many seasons in succession upon soil which has become so exhausted 

 as to yield little or no return when planted with leguminous or root 

 crops. They, however, appear to depend for their nitrogen entirely 

 upon nitrates in the soil, and as their growth is practically over before 

 the great season for nitrification begins, they derive great benefit from 

 nitrogenous manures. 



Wheat (Triticum vulgare), being usually autumn sown, has a longer 

 period of growth than barley or oats and is consequently better able to 

 supply itself with the necessary food from the soil. With a wheat 

 crop, however, the land loses the spring tillage, which is conducive to 

 nitrification, and therefore nitrogenous manures are perhaps more 

 required by wheat than by the other cereals. 



Wheat straw is remarkable for the excessively large amount of 

 silica and small amount of nutritive matter which it often contains. 



Wheat is particularly fitted for human food owing to the light, spongy 

 and palatable bread which can be made from wheat flour. This is due 

 to the richness of the grain in gluten and the peculiarity of this gluten 

 as compared with that occurring in the other cereals. 



According to Osborne and Voorhees, the proteids of the wheat 

 grain consist mainly of gliadin and glutenin, together with smaller 

 quantities of a globulin, an albumin and a proteose. The average 

 nitrogen content of these proteids is 17 '6, so that the factor for con- 

 verting nitrogen into proteid in the case of wheat should be, not 6 '25, 

 but only 5*68. If this were adopted it would diminish the proteid item 

 in analyses and correspondingly increase the soluble carbohydrates. On 

 hydrolysis, the wheat proteids yield relatively large amounts of glutamic 

 acid, proline and leucine, but small quantities of lysine and arginine ; 

 tryptophane and histidine are present and a considerable amount of 

 ammonia. 



The proportion of total protein in wheat varies considerably, spring 

 wheat containing more than winter varieties, hard or durum wheats also 

 being high in protein content. Climate, too, has an enormous influence 

 upon the proportion of protein in the grain ; samples grown from the 

 same seed in different districts often show a variation of 50 per cent in 

 their protein content. 



The analyses given of wheat from various countries (p. 236), com- 

 piled by Konig, will indicate the sort of variations shown. 



The actual amounts of moisture found are given in the following 

 table but the figures for all other constituents are calculated to a 

 basis of 13'37 per cent of moisture, so as to render comparison easier. 



In the case of wheat grown in Kansas, a protein content of 22 per 

 cent is by no means uncommon ; such wheats are hard and horny, 

 while in England and Scotland, where the plant takes longer to mature, 

 the grain is soft and starchy and may contain as low as 10, or even 

 less, per cent of proteins. 



The " strength " of wheat flour, i.e., its capacity for yielding large 



